Does "Recursive Collections" Create Duplicates?
Suppose I have Collection A with Subcollection B and Subcollection C. When recursive collections is set to TRUE does importing item X to Subcollection B and then (separately) importing item X to Subcollection C lead to a duplicate of item X in Collection A? I am not entirely sure based on my own imports. Does it matter if item X is imported to the sub collections or instead I manually create item X in Subcollection B then copy it to Subcollection C?
If you import an item once into one collection and import it again in _any_ collection or subcollection you will have duplicated the item in your library.
Collections are like playlists not like directories on a computer file system. The same item can be placed in more than one collection or it can remain in your library without assignment to a collection.
However, if you are concerned with groups that is a somewhat different issue.